Vehicle driving assist device

ABSTRACT

A vehicle driving assist device comprises a risk determination region setting unit configured to set a risk determination region for calculating a risk degree that decreases as a distance outward from a center of the oncoming moving body in a width direction of the oncoming moving body increases. The risk determination region setting unit is further configured to set the risk determination region such that the risk degree is zero at a distance in a vehicle width direction between the vehicle and the oncoming moving body matching an average distance. The average distance is calculated based on distances in the vehicle width direction between the vehicle and oncoming moving bodies acquired every time the vehicle passes by the oncoming moving bodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2022-008967 filed on Jan. 24, 2022, the entire contents of which arehereby incorporated by reference.

BACKGROUND

The disclosure relates to a vehicle driving assist device having afunction of performing collision avoidance control in response to anobstacle.

In vehicles such as an automobile, driving assist devices for assistingdriving operations of a driver have been put to practical use for thepurpose of alleviating a burden of the driving operations of the driverand achieving improvements in safety. With this type of driving assistdevice, various driving modes are set. These driving modes include, forexample, a manual driving mode for performing steering andacceleration/deceleration in accordance with independent drivingoperations by the driver, a driving assist mode for performing steeringassist control and acceleration/deceleration control on the premise ofindependent driving operations by the driver, and a driving assist modefor causing a vehicle to travel without using any driving operations bythe driver (so-called automatic driving mode).

The driving assist control in each of the driving assist modes isbasically realized by providing an adaptive cruise control (ACC)function and an active lane keep centering (ALKC) control function, andthe like. With such driving assist control, the vehicle can be caused totravel along a traveling lane while maintaining an inter-vehicledistance from a preceding vehicle.

Further, as a technique related to active safety of the driving assistdevice, various proposals have been made for performing collisionavoidance control with an obstacle present on a traveling path ahead ofthe host vehicle (refer to, for example, Japanese Unexamined PatentApplication Publication (JP-A) No. 2016-224501). In the technique ofJP-A No. 2016-224501, a collision predictor identifies an expectedcollision region with an obstacle from a traveling trajectory (targettraveling path) of the host vehicle and a position, a shape, a movementdirection, and the like of the obstacle. Further, the collisionpredictor integrates a collision probability value of collision with theobstacle in an expected collision region. Then, in a case where anintegrated value of the collision probability value becomes large in oneor more expected collision regions identified at points in time, acollision determination unit generates an alert signal.

SUMMARY

An aspect of the disclosure provides a vehicle driving assist devicecomprising: a traveling environment recognizer configured to recognizetraveling environment information outside a vehicle; an obstaclerecognizer configured to recognize, based on the traveling environmentinformation, an obstacle present on a target traveling path of thevehicle; an emergency collision avoidance controller configured to, upondetermination that the vehicle is highly likely to collide with theobstacle, perform emergency collision avoidance control for avoiding acollision of the vehicle with the obstacle; an oncoming moving bodyrecognizer configured to recognize, based on the traveling environmentinformation, oncoming moving bodies and an oncoming moving body each ofwhich moves in an oncoming lane adjacent to a traveling lane of thevehicle and each of which has a velocity component in a directionopposite to a traveling direction of the vehicle, the oncoming movingbodies including an oncoming moving body; a risk determination regionsetting unit configured to set a risk determination region forcalculating a risk degree that decreases as a distance outward from acenter of the oncoming moving body in a width direction of the oncomingmoving body increases; a risk degree calculator configured to calculatethe risk degree for the oncoming moving body in accordance with anoverlap state between the target traveling path of the vehicle and therisk determination region; a preliminary collision avoidance controllerconfigured to recognize the oncoming moving body as the obstacle inaccordance with the risk degree, and perform preliminary collisionavoidance control in response to the oncoming moving body recognized asthe obstacle prior to the emergency collision avoidance control; and anaverage distance calculator configured to, when the preliminarycollision avoidance control is turned off, acquire distances in avehicle width direction between the vehicle and the oncoming movingbodies every time the vehicle passes by the oncoming moving bodies, andcalculate an average distance of the distances in the vehicle widthdirection. The risk determination region setting unit is furtherconfigured to set the risk determination region such that the riskdegree calculated by the risk degree calculator is zero at a distance inthe vehicle width direction between the vehicle and the oncoming movingbody matching the average distance.

An aspect of the disclosure provides a vehicle driving assist devicecomprising one or more ECUs configured to: recognize travelingenvironment information outside a vehicle; recognize, based on thetraveling environment information, an obstacle present on a targettraveling path of the vehicle; upon determination that the vehicle ishighly likely to collide with the obstacle, perform emergency collisionavoidance control for avoiding a collision of the vehicle with theobstacle; recognize, based on the traveling environment information,oncoming moving bodies and an oncoming moving body each of which movesin an oncoming lane adjacent to a traveling lane of the vehicle and eachof which has a velocity component in a direction opposite to a travelingdirection of the vehicle, the oncoming moving bodies including anoncoming moving body; set a risk determination region for calculating arisk degree that decreases as a distance outward from a center of theoncoming moving body in a width direction of the oncoming moving bodyincreases; calculate the risk degree for the oncoming moving body inaccordance with an overlap state between the target traveling path ofthe vehicle and the risk determination region; recognize the oncomingmoving body as the obstacle in accordance with the risk degree, andperform preliminary collision avoidance control in response to theoncoming moving body recognized as the obstacle prior to the emergencycollision avoidance control; and acquire, when the preliminary collisionavoidance control is turned off, distances in a vehicle width directionbetween the vehicle and the oncoming moving bodies every time thevehicle passes by the oncoming moving bodies, and calculate an averagedistance of the distances in the vehicle width direction. The one ormore ECUs are further configured to set the risk determination regionsuch that the risk degree is zero at a distance in the vehicle widthdirection between the vehicle and the oncoming moving body matching theaverage distance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification. The drawings illustrate an exampleembodiment and, together with the specification, serve to describe theprinciples of the disclosure.

FIG. 1 is a schematic configuration diagram of a driving assist device.

FIG. 2 is an explanatory view illustrating a monitoring region of astereo camera and radar.

FIG. 3 is an explanatory view illustrating an obstacle present on atarget traveling path ahead of the host vehicle.

FIG. 4 is an explanatory view illustrating an oncoming moving bodypresent in an oncoming lane.

FIG. 5 is an explanatory view illustrating a risk determination region.

FIG. 6 is an explanatory view illustrating a relationship between atarget traveling path of the host vehicle and the risk determinationregion of the oncoming moving body.

FIG. 7 is an explanatory view illustrating a distance in a vehicle widthdirection when the host vehicle and the oncoming moving body pass byeach other.

FIG. 8 is a flowchart illustrating an average distance calculationroutine for calculating an average distance in the vehicle widthdirection to the oncoming moving body.

FIG. 9 is a flowchart illustrating a preliminary collision avoidancecontrol routine.

FIG. 10 is a flowchart illustrating a risk degree calculationsubroutine.

FIG. 11 is a flowchart illustrating a risk degree upper limit processingsubroutine.

FIG. 12 is a flowchart illustrating a risk degree reduction processingsubroutine.

FIG. 13 is a flowchart illustrating a forced control interventiondetermination subroutine.

FIG. 14 is an explanatory view illustrating a case where a risk degreeof the oncoming moving body increases due to a factor other thanwandering.

FIG. 15 is an explanatory view illustrating a case where the risk degreeof the oncoming moving body increases due to a factor other thanwandering.

FIG. 16 is an explanatory view illustrating a case where the risk degreeof the oncoming moving body increases due to a factor other thanwandering.

FIG. 17 is an explanatory view illustrating control contents ofpreliminary collision avoidance control.

DETAILED DESCRIPTION

An oncoming vehicle or the like traveling in an oncoming lane adjacentto a host vehicle traveling lane is basically present at a positionseparated in a vehicle width direction from a target traveling path ofthe host vehicle. Accordingly, the oncoming vehicle or the like may notbe an applicable target of collision avoidance control. In this case,for example, in a case where the oncoming vehicle or the like suddenlyenters the traveling lane of the host vehicle due to the inattentivenessor the like of the driver driving the oncoming vehicle or the like, itmay be difficult to realize sufficient collision avoidance control inresponse to the oncoming vehicle.

It is desirable to provide a vehicle driving assist device that canensure sufficient safety even in a case where an oncoming vehicle or thelike suddenly enters a traveling lane of a host vehicle.

In the following, an embodiment of the disclosure is described in detailwith reference to the accompanying drawings. Note that the followingdescription is directed to an illustrative example of the disclosure andnot to be construed as limiting to the disclosure. Factors including,without limitation, numerical values, shapes, materials, components,positions of the components, and how the components are coupled to eachother are illustrative only and not to be construed as limiting to thedisclosure. Further, elements in the following example embodiment whichare not recited in a most-generic independent claim of the disclosureare optional and may be provided on an as-needed basis. The drawings areschematic and are not intended to be drawn to scale. Throughout thepresent specification and the drawings, elements having substantiallythe same function and configuration are denoted with the same numeralsto avoid any redundant description.

As illustrated in FIGS. 1 and 2 , a driving assist device 1 includes acamera unit 10 fixed to an upper center of a front part in a cabin of avehicle (host vehicle) M, for example.

This camera unit 10 includes a stereo camera 11, an image processingunit (IPU) 12, an image recognition unit (image recognition_ECU) 13, anda traveling control unit (travel_ECU) 14.

The stereo camera 11 includes a main camera 11 a and a sub-camera 11 b.The main camera 11 a and the sub-camera 11 b are each constituted by acomplementary metal-oxide semiconductor (CMOS), for example.

The main camera 11 a and the sub-camera 11 b are disposed in left-rightsymmetric positions across a center in a vehicle width direction.

The main camera 11 a and the sub-camera 11 b capture stereo images of atraveling environment in a region Af (refer to FIG. 2 ) in front andoutside of the host vehicle from different viewpoints. Image capturingcycles of the main camera 11 a and sub-camera 11 b are synchronized witheach other.

The IPU 12 performs predetermined image processing on travelingenvironment images captured by the stereo camera 11. The IPU 12 thusdetects edges of various objects represented in the images, such assolid objects or lane markers on a road surface. Then, the IPU 12 findsdistance information from a position deviation amount of thecorresponding edges in the left and right images. In this way, the IPU12 generates image information (distance image information) includingdistance information.

On the basis of the distance image information and the like receivedfrom the IPU 12, the image recognition_ECU 13 determines the roadcurvature (1/m) of the lane markers defining the left and right sides ofthe lane in which the host vehicle M is traveling (host vehicletraveling path), and the width between the left and right lane markers(lane width). Further, the image recognition_ECU 13 determines the roadcurvature of the lane markers defining the left and right sides of alane or the like adjacent to the lane in which the host vehicle M istraveling, and the width between the left and right lane markers.Various methods of determining the curvatures and the lane widths areknown. For example, the image recognition_ECU 13 performs binarizationprocessing based on luminance for each pixel on a distance image. As aresult, the image recognition_ECU 13 extracts lane marker candidatepoints on the road. Further, the image recognition_ECU 13 performs curveapproximation by the least-squares method or the like on a pointsequence of the extracted lane marker candidate points. The imagerecognition_ECU 13 thus determines the curvatures of the left and rightlane markers for each predetermined section. Furthermore, the imagerecognition_ECU 13 calculates the lane width from the difference betweenthe curvatures of both the left and right lane markers.

Then, the image recognition_ECU 13 calculates a lane center, a lateralposition deviation of the host vehicle, and the like on the basis of thecurvatures of the left and right lane markers and the lane width.Herein, the lateral position deviation of the host vehicle is a distancefrom the lane center to the center of the host vehicle M in the vehiclewidth direction.

Further, the image recognition_ECU 13 performs predetermined patternmatching or the like on the distance image information. The imagerecognition_ECU 13 thus recognizes solid objects, such as a guardrail, acurb, a median strip, and nearby vehicles present along the road.Herein, upon recognizing the solid object, the image recognition_ECU 13recognizes, for example, a type of the solid object, a distance to thesolid object, a velocity of the solid object, and a relative velocitybetween the solid object and the host vehicle M.

Each of the various types of information recognized in the imagerecognition_ECU 13 is output to a travel_ECU 14 as traveling environmentinformation.

As described above, the image recognition_ECU 13 recognizes thetraveling environment information outside the vehicle. In oneembodiment, along with the stereo camera 11 and the IPU 12, the imagerecognition_ECU 13 may serve as a “traveling environment recognizer”.

The travel_ECU 14 is a control unit for comprehensively controlling thedriving assist device 1.

This travel_ECU 14 is coupled, via an in-vehicle communication line suchas a controller area network (CAN), to various control units. Thevarious control units include a cockpit control unit (CP_ECU) 21, anengine control unit (E/G_ECU) 22, a transmission control unit (T/M_ECU)23, a braking control unit (BK_ECU) 24, and a power steering controlunit (PS_ECU) 25.

Furthermore, the travel_ECU 14 is coupled to various types of sensorsincluding a locator unit 36, a left front side sensor 371 f, a rightfront side sensor 37 rf, a left rear side sensor 371 r, and a right rearside sensor 37 rr.

The CP_ECU 21 is coupled to a human machine interface (HMI) 31 disposedaround the driver’s seat. The HMI 31 includes, for example, operationswitches for setting and executing various types of driving assistcontrols and the like, a mode switch for switching the driving assistmode, a steering touch sensor that detects a steering state of thedriver, a turn signal switch, a driver monitoring system (DMS) thatperforms facial recognition, eye detection, or the like of the driver, atouch panel type display, a combination meter, and a speaker.

The CP_ECU 21, upon receiving a control signal from the travel_ECU 14,notifies the driver, as appropriate, of various types of alerts relatedto a preceding vehicle or the like, an implementation state of thedriving assist control, and various information related to the travelingenvironment and the like of the host vehicle M, by display, audio, orthe like through the HMI 31.

Further, the CP_ECU 21 outputs various input information to thetravel_ECU 14, such as an on or off operation state of each of thevarious driving assist controls input by the driver through the HMI 31,a vehicle velocity Vs set for the host vehicle M (set vehicle velocity),an operation state of a turn signal switch, and an ID of the driverfacially recognized in the DMS.

The E/G_ECU 22 is coupled, at its output side, to a throttle actuator 32of an electronic control throttle or the like. Further, the E/G_ECU 22is coupled, at its input side, to various sensors such as an acceleratorsensor (not illustrated).

The E/G_ECU 22 controls the driving of the throttle actuator 32 on thebasis of control signals from the travel _ECU 14, detection signals fromvarious sensors, or the like. This causes the E/G_ECU 22 to adjust anamount of intake air of the engine and generate a desired engine output.Further, the E/G_ECU 22 outputs signals of an accelerator pedal positionand the like detected by the various sensors to the travel_ECU 14.

The T/M_ECU 23 is coupled, at its output side, to a hydraulic controlcircuit 33. Further, the T/M_ECU 23 is coupled, at its input side, tovarious sensors such as a shift position sensor (not illustrated). TheT/M_ECU 23 performs hydraulic control for the hydraulic control circuit33 on the basis of an engine torque signal estimated by the E/G_ECU 22,detection signals from various sensors, and the like. Thus, the T/M_ECU23 operates frictional engagement elements, pulleys, and the likeprovided in an automatic transmission, and causes the engine output toshift at a desired transmission ratio. Further, the T/M_ECU 23 outputssignals of a shift position and the like detected by various sensors tothe travel_ECU 14.

The BK_ECU 24 is coupled, at its output side, to a brake actuator 34.The brake actuator 34 adjusts the brake fluid pressure to be fed tobrake wheel cylinders provided for respective wheels. Further, theBK_ECU 24 is coupled, at its input side, to various sensors such as abrake pedal sensor, a yaw rate sensor, front/rear acceleration sensors,and a vehicle speed sensor (not illustrated).

The BK_ECU 24 controls the driving of the brake actuator 34 on the basisof control signals from the travel_ECU 14 or detection signals fromvarious sensors. The BK_ECU 24 thus generates, at each wheel, a brakingforce for performing forced braking control, yaw rate control, and thelike on the host vehicle M, as appropriate. Further, the BK_ECU 24outputs signals of a brake operation state, a yaw rate, aforward/reverse acceleration, a vehicle velocity (host vehiclevelocity), and the like detected by various sensors to the travel _ECU14.

The PS_ECU 25 is coupled, at its output side, to an electric powersteering motor 35. The electric power steering motor 35 applies asteering torque to a steering mechanism by a rotational force of themotor. Further, the PS_ECU 25 is coupled, at its input side, to varioussensors such as a steering torque sensor and a steering angle sensor.

The PS_ECU 25 controls the driving of the electric power steering motor35 on the basis of control signals from the travel_ECU 14 or detectionsignals from various sensors. As a result, the PS_ECU 25 generates asteering torque for the steering mechanism. Further, the PS_ECU 25outputs signals of the steering torque, a steering angle, and the likedetected by various sensors to the travel_ECU 14.

The locator unit 36 includes a global navigation satellite system (GNSS)sensor 36 a and a high-precision road map database (road map DB) 36 b.

The GNSS sensor 36 a receives positioning signals transmitted frompositioning satellites, and thus measures a position (latitude,longitude, altitude, and the like) of the host vehicle M.

The road map DB 36 b is a large-capacity storage medium such as a harddisk drive (HDD). This road map DB 36 b stores high-precision road mapinformation (a dynamic map). The road map information includes, forexample, lane width data, lane center position coordinate data, azimuthangle data of the lane, and speed limit data, as lane data whenperforming automatic driving. The lane data is stored for each lane onthe road map at an interval of several meters. On the basis of a requestsignal from the travel_ECU 14, the road map DB 36 b outputs to thetravel_ECU 14, as the traveling environment information, road mapinformation of a set range based on the host vehicle position measuredby the GNSS sensor 36 a, for example.

As describe above, the road map DB 36 b recognizes the travelingenvironment information outside the vehicle. In one embodiment, alongwith the GNSS sensor 36 a, the road map DB 36 b may serve a “travelingenvironment recognizer”.

The left front side sensor 371 f and the right front side sensor 37 rfare each constituted by, for example, a millimeter wave radar. The leftfront side sensor 371 f and the right front side sensor 37 rf aredisposed respectively on the left and right sides of a front bumper, forexample. The left front side sensor 371 f and the right front sidesensor 37 rf detect, as the traveling environment information, solidobjects present in regions Alf, Arf (refer to FIG. 2 ) that are left andright oblique front and side regions of the host vehicle M and difficultto recognize in images of the stereo camera 11.

The left rear side sensor 371 r and the right rear side sensor 37 rr areeach constituted by, for example, a millimeter wave radar. The left rearside sensor 371 r and the right rear side sensor 37 rr are disposedrespectively on left and right sides of a rear bumper, for example. Theleft rear side sensor 371 r and the right rear side sensor 37 rr detect,as the traveling environment information, solid objects present inregions Alr, Arr (refer to FIG. 2 ) that are left and right oblique rearand side regions of the host vehicle M and difficult to recognize by theleft front side sensor 371 f and the right front side sensor 37 rf.

Herein, in a case where each sensor is constituted by a millimeter waveradar, the millimeter wave radar detects mainly a solid object such as aparallel traveling vehicle, a following vehicle, or the like byanalyzing reflected waves reflected by an object with respect to theelectric waves output from the millimeter wave radar. In one example,each radar detects, as information related to the solid object, thelateral width of the solid object, the position of a representativepoint of the solid object (relative position with respect to the hostvehicle M), the velocity of the solid object, and the like.

As describe above, the left front side sensor 371 f, the right frontside sensor 37 rf, the left rear side sensor 371 r, and the right rearside sensor 37 rr recognizes the traveling environment informationoutside the vehicle. In one embodiment, the left front side sensor 371f, the right front side sensor 37 rf, the left rear side sensor 371 r,and the right rear side sensor 37 rr may serve as a “travelingenvironment recognizer”.

Note that coordinates of each target outside the vehicle included in thetraveling environment information recognized by the imagerecognition_ECU 13, the locator unit 36, the left front side sensor 371f, the right front side sensor 37 rf, the left rear side sensor 371 r,and the right rear side sensor 37 rr are converted to coordinates of athree-dimensional coordinate system (refer to FIG. 2 ) in which thecenter of the host vehicle M is set as the origin, for example, in thetravel_ECU 14.

The driving modes set in the travel_ECU 14 include a manual drivingmode, a first travel control mode and a second travel control mode asmodes for travel control, and a safe stop mode. These driving modes areeach selectively switchable in the travel_ECU 14 on the basis of, forexample, the operation status of the mode switch provided to the HMI 31,for example.

Herein, the manual driving mode is a driving mode in which the driverholds the steering wheel. That is, the manual driving mode is a drivingmode in which the driver causes the host vehicle M to travel inaccordance with driving operations such as a steering operation, anacceleration operation, and a braking operation, for example.

Similarly, the first travel control mode is a driving mode in which thedriver holds the steering wheel.

That is, the first travel control mode is a so-called semi-automateddriving mode in which the host vehicle M is caused to travel whilereflecting the driving operations by the driver. This first travelcontrol mode is realized by, for example, the travel_ECU 14 outputtingvarious control signals to the E/G_ECU 22, the BK_ECU 24, and the PS_ECU25. In the first travel control mode, mainly adaptive cruise control(ACC), active lane keep centering (ALKC) control, active lane keepbouncing (ALKB) control, lane change control, and the like are performedin combination as appropriate. This makes it possible for the hostvehicle M to travel along the target traveling path. Furthermore, in thefirst travel control mode, the lane change control can be performed whenthe turn signal switch is operated by the driver.

Herein, the adaptive cruise control is basically performed on the basisof the traveling environment information input from the imagerecognition_ECU 13 or the like.

In one example, in a case where a preceding vehicle is recognized aheadof the host vehicle M by the image recognition_ECU 13 or the like, thetravel_ECU 14 performs adaptive travel control as a part of the adaptivecruise control. In this adaptive travel control, the travel_ECU 14 setsa target inter-vehicle distance Lt and a target vehicle velocity Vt onthe basis of a vehicle velocity V1 of the preceding vehicle or the like.Then, the travel_ECU 14 performs acceleration/deceleration control forthe host vehicle M on the basis of the target inter-vehicle distance Ltand the target vehicle velocity Vt. In this way, the travel_ECU 14basically causes the host vehicle M to travel following the precedingvehicle in a state of maintaining a vehicle velocity V at the targetvehicle velocity Vt while maintaining an inter-vehicle distance L at thetarget inter-vehicle distance Lt.

On the other hand, for example, in a case where no preceding vehicle isrecognized ahead of the host vehicle M by the image recognition_ECU 13or the like, the travel_ECU 14 performs constant velocity travel controlas a part of the adaptive cruise control. In this constant velocitytravel control, the travel_ECU 14 sets the set vehicle velocity Vs inputby the driver as the target vehicle velocity Vt. Then, the travel_ECU 14performs acceleration/deceleration control for the host vehicle M on thebasis of the target vehicle velocity Vt. In this way, the travel_ECU 14maintains the vehicle velocity V of the host vehicle M at the setvehicle velocity Vs.

Further, the active lane keep centering control and the active lane keepbouncing control are basically performed on the basis of the travelingenvironment information input from at least one of the imagerecognition_ECU 13 or the locator unit 36. That is, the travel_ECU 14sets a target traveling path Rm at the center of the host vehicletraveling lane along the left and right lane markers on the basis of,for example, the lane marker information or the like included in thetraveling environment information. Then, the travel_ECU 14 keeps thehost vehicle M in the center of the lane by performing feed-forwardcontrol, feed-back control, and the like for steering on the basis ofthe target traveling path Rm. Further, upon determination that the hostvehicle M is likely to deviate from the host vehicle traveling lane dueto the influence of a lateral wind, a cant of the road, or the like, thetravel_ECU 14 suppresses the lane deviation by forced steering control.

Further, lane change control is basically performed on the basis of thetraveling environment information input from the image recognition_ECU13, the left front side sensor 371 f, the right front side sensor 37 rf,the left rear side sensor 371 r, and the right rear side sensor 37 rr.This lane change control is executed when, for example, the turn signalswitch is operated by the driver. That is, the travel_ECU 14 recognizesan adjacent lane present in the operation direction of the turn signalswitch on the basis of the traveling environment information. Further,the travel_ECU 14 recognizes whether a vehicle or the like that inhibitsa lane change is present in the adj acent lane. Then, the travel_ECU 14,upon determination that space exists for a lane change in the adjacentlane, performs the lane change to the adjacent lane. This lane changecontrol is performed in coordination with the adaptive cruise control.

The second travel control mode is a driving mode in which the hostvehicle M is caused to travel without driving operation by the driver,that is, without holding the steering wheel or performing anacceleration operation or a braking operation. That is, the secondtravel control mode is a so-called automatic driving mode in which thehost vehicle M is caused to travel autonomously without drivingoperation by the driver. This second travel control mode is realized by,for example, the travel_ECU 14 outputting various control signals to theE/G_ECU 22, the BK_ECU 24, and the PS_ECU 25. In the second travelcontrol mode, mainly preceding-vehicle adaptive control, active lanekeep centering control, active lane keep bouncing control, and the likeare performed in combination as appropriate.

This makes it possible for the host vehicle M to travel along the targetroute (route map information). Furthermore, in the second travel controlmode, lane change control can also be performed. Note that, in thesecond travel control mode, lane change control is performedautomatically, as appropriate, not only when the turn signal switch isoperated by the driver, but also in accordance with a travel route up toa destination set in the host vehicle M, traveling environmentinformation, and the like.

The safe stop mode is a mode for automatically stopping the host vehicleM at a side strip or the like. This safe stop mode is executed, forexample, in a case where the traveling based on the second travelcontrol mode becomes uncontinuable during the traveling in the secondtravel control mode, and the driver fails to take over the drivingoperation, for example (that is, where the second travel control modecannot transition to the manual driving mode or to the first travelcontrol mode).

Further, in each of the driving modes described above, the travel_ECU 14performs emergency collision avoidance control, as appropriate, for anobstacle such as a vehicle that is highly likely to collide with thehost vehicle M. This emergency collision avoidance control includes, forexample, emergency braking (autonomous emergency braking (AEB)) controland emergency steering control.

The emergency braking control is basically control for avoiding acollision with an obstacle present in the target traveling path Rm aheadof the host vehicle M by braking. In the emergency braking control, thetravel_ECU 14 sets, for example, a target traveling region Am ahead ofthe host vehicle M, as illustrated in FIG. 3 . This target travelingregion Am includes a predetermined width (greater than or equal to thevehicle width of the host vehicle M, for example) centered on the targettraveling path Rm. Further, the travel unit_ECU 14 detects an obstaclesuch as a preceding vehicle, a stopped vehicle, or the like present inthe target traveling region Am on the basis of the traveling environmentinformation. Furthermore, the travel_ECU 14 calculates, as a predictedcollision time with the obstacle, a time-to-collision (longitudinaltime-to-collision) TTCz in a front-rear direction of the host vehicle M.This longitudinal time-to-collision TTCz is calculated on the basis of arelative velocity and a relative distance between the host vehicle M andthe obstacle.

Then, the travel_ECU 14 executes primary braking control when thelongitudinal time-to-collision TTCz becomes less than a first thresholdvalue Tth1 set in advance. When the primary braking control is started,the travel_ECU 14 decelerates the host vehicle M by using a first targetdeceleration a1 (0.4 G, for example) set in advance.

Further, the travel_ECU 14 executes secondary braking control when thelongitudinal time-to-collision TTCz is less than a second thresholdvalue Tth2 (where Tth2 < Tth1) set in advance. When secondary brakingcontrol is started, the travel_ECU 14 decelerates the host vehicle Muntil the relative velocity relative to the obstacle is “0” by using asecond target deceleration a2 (1 G, for example) set in advance.

Emergency steering control is control for avoiding a collision with anobstacle present in the target traveling path ahead of the host vehicleM by steering. Upon determination that collision with the obstaclecannot be avoided by, for example, secondary braking control, thetravel_ECU 14 executes emergency steering control instead of or inconjunction with emergency braking control.

In one example, the travel_ECU 14 executes emergency steering control(refer to a host vehicle M′ in FIG. 3 , for example) when thelongitudinal time-to-collision TTCz is less than a third threshold valueTth3 (where Tth3 < Tth2) set in advance.

In this emergency steering control, the travel_ECU 14 sets a targetlateral position to the side of the obstacle. Further, the travel_ECU 14sets a new target traveling path Ravo for causing the host vehicle M toreach the target lateral position. This new target traveling path Ravois set by, for example, creating two sections: a steering away sectionfor causing the host vehicle M to head toward the side of the obstacle,and a steering back section for returning an orientation of the hostvehicle M to a direction along the host vehicle traveling path. Then,the travel unit_ECU 14 executes steering control along the new targettraveling path Ravo.

Note that the travel_ECU 14 may variably set each of the first to thirdthreshold values Tth1 to Tth3 in accordance with an overlap ratio of theobstacle to the host vehicle M in the vehicle width direction. Thisoverlap ratio Rr is calculated, for example, on the basis of an amountby which the obstacle enters the target traveling region Am. Then, thetravel _ECU 14 sets each threshold value so that the first to thirdthreshold values Tth1 to Tth3 increase as the overlap ratio Rr increasesby using a map or the like set in advance, for example.

However, when the host vehicle M is traveling on a road in which amedian strip is not present, a case is expected where an oncoming movingbody O present in the oncoming lane suddenly enters the traveling laneof the host vehicle M. Here, in the present embodiment, the oncomingmoving body O refers to an oncoming vehicle (including a two-wheeledvehicle), a pedestrian, or the like that moves with a velocity componentin a direction opposite to the movement direction of the host vehicle M.To realize collision avoidance with such an oncoming moving body O, thetravel_ECU 14 of the present embodiment extends and applies emergencycollision avoidance control in response to the oncoming moving body Oentering the traveling lane of the host vehicle M from the oncoming laneof the road without the median strip.

Prior to the emergency collision avoidance control targeting theoncoming moving body O, the travel_ECU 14 performs, as appropriate,preliminary collision avoidance control, as necessary. This preliminarycollision avoidance control is control for suppressing a risk ofcollision of the host vehicle M with the oncoming moving body O inadvance.

The preliminary collision avoidance control can be turned on or off, asappropriate, by the driver operating an operation switch provided in theHMI 31, for example.

To execute the preliminary collision avoidance control, the travel_ECU14 determines, on the basis of the traveling environment information,whether a median strip that divides the road into the traveling lane ofthe host vehicle M and the oncoming lane is present on the road. Then,in a case where a median strip is not present on the road traveled bythe host vehicle M, the travel_ECU 14 detects the oncoming moving body Omoving in the oncoming lane, for example (refer to FIG. 4 ). Upondetection of the oncoming moving body O, the travel_ECU 14 calculates,on the basis of a velocity Vo of the oncoming moving body O, alongitudinal velocity component Voz and a lateral velocity component Voxcorresponding to the front-rear direction and the vehicle widthdirection of the host vehicle M.

Further, the travel_ECU 14 calculates, as predicted collision times forthe oncoming moving body O, the time-to-collision (longitudinaltime-to-collision) TTCz in the front-rear direction of the host vehicleM and a time-to-collision (lateral time-to-collision) TTCx in thevehicle width direction of the host vehicle M.

That is, for example, the travel_ECU 14 calculates the longitudinaltime-to-collision TTCz by dividing a relative velocity in thelongitudinal direction calculated from the vehicle velocity V of thehost vehicle M and the longitudinal velocity component Voz of theoncoming moving body O by a relative distance between the host vehicle Mand the oncoming moving body O in the longitudinal direction.

Further, the travel_ECU 14 calculates the lateral time-to-collision TTCxby, for example, dividing the lateral velocity component Vox of theoncoming moving body O by a distance from the oncoming moving body O tothe target traveling region Am. In the calculation of this lateraltime-to-collision TTCx, in some embodiments, the distance from theoncoming moving body O to the target traveling region Am is corrected onthe basis of a width of the oncoming moving body O and an entry angle(predicted collision angle) of the oncoming moving body O with respectto the target traveling region Am.

Furthermore, the travel_ECU 14 calculates a risk degree as a parameterindicating a likelihood (risk) of the oncoming moving body O collidingwith the host vehicle M.

In calculating this risk degree, the travel_ECU 14 sets a riskdetermination region. This risk determination region is configured toextend in the width direction from the center of the oncoming movingbody O. The risk determination region is a region for calculating a riskdegree R that differs in value depending on a distance outward from thecenter of the oncoming moving body O in the width direction of theoncoming moving body O, as illustrated in FIGS. 5 and 6 , for example.For example, in the risk determination region illustrated in FIGS. 5 and6 , four small regions including a “danger region,” a “warning region,”a “caution region,” and a “safe region” are set in this order from thevicinity of the oncoming moving body O.

Then, in each of the small regions, the risk degrees R of “1,” “0.75,”“0.25,” and “0” are set with the risk degree R decreasing stepwise asthe distance from the oncoming moving body O increases.

Upon setting the risk determination region, the travel_ECU 14 calculatesthe risk degree R for the oncoming moving body O in accordance with anoverlap state of the target traveling path Rm of the host vehicle M andthe risk determination region. That is, the travel_ECU 14 sets the riskdegree R of the small region penetrated by the target traveling path Rmas the risk degree R for the current oncoming moving body O. Asunderstood from FIG. 6 as well, the risk degree R increases as theoncoming moving body O moves toward the traveling lane of the hostvehicle M due to wandering of the oncoming moving body O or the like.Factors that may cause the oncoming moving body O to wander include, forexample, the driver driving the oncoming moving body O falling asleep,looking aside, or executing a wrong operation.

Furthermore, in some embodiments, the travel_ECU 14 calculates acumulative value of the risk degree obtained by performing predeterminedweighting on the risk degrees R up to the present time for the oncomingmoving body O (hereinafter referred to as risk degree Rc). This riskdegree Rc can be calculated by equation (1), for example. “Rc = (1 - α)R_(t)+ αRc_(t-1)” ... (1)

Note that, in equation (1), α is a weighting factor. Further, inequation (1), Rt is the current risk degree calculated from the riskdetermination region. Further, in equation (1), Rc_(t-1) is thecumulative value of the risk degrees calculated up to the previouscalculation.

On the basis of the risk degree Rc thus calculated, the travel_ECU 14determines whether the oncoming moving body O is an obstacle that islikely to collide with the host vehicle M. Then, upon recognizing theoncoming moving body O as an obstacle, the travel_ECU 14 executes, asappropriate, preliminary collision avoidance control prior to emergencycollision avoidance control in response to the oncoming moving body O.

Preliminary collision avoidance control is preliminary control forcausing emergency collision avoidance control to function more safely.Thus, preliminary collision avoidance control is generally started at atiming prior to the oncoming moving body O approaching the immediatevicinity of the host vehicle M. Accordingly, depending on the timing atwhich preliminary collision avoidance control is started, thepreliminary collision avoidance control may cause the driver to feel asense of discomfort.

Therefore, the travel_ECU 14 variably sets the risk determination regionfor the oncoming moving body O so that the timing at which preliminarycollision avoidance control is started matches the feeling of thedriver. In one example, the travel_ECU 14 acquires, as informationindicating the feeling of each driver, a distance x between the hostvehicle M and oncoming moving bodies O in the vehicle width directionevery time the host vehicle M passes by the oncoming moving bodies O(refer to FIG. 7 ). Then, the travel_ECU 14 learns an average distanceXave of the acquired distances x. Such acquisition of the distance x andcalculation of the average distance Xave are performed in a case where,for example, manual driving mode is selected as the driving mode andpreliminary collision avoidance control is turned off.

Then, in a case where preliminary collision avoidance control is on, thetravel_ECU 14 variably sets the risk determination region on the basisof the average distance Vave calculated for each driver. For example,the travel_ECU 14 multiplies the risk determination region (riskdetermination reference region) that is a reference set in advance by anincrease/decrease ratio corresponding to the average distance Xave. Inthis way, the travel_ECU 14 sets the risk determination region so thatthe distance x between the host vehicle M and the oncoming moving body Oin the vehicle width direction matches the average distance Xave and thecalculated risk degree R becomes “0”, for example.

In one embodiment, the travel_ECU 14 serves as “obstacle recognizer,”“an emergency collision avoidance controller,” an “oncoming moving bodyrecognizer,” a “risk determination region setting unit,” a “risk degreecalculator,” a “preliminary collision avoidance controller,” and an“average distance calculator”.

Next, the calculation processing of the average distance Xave betweenthe host vehicle M and the oncoming moving bodies O in the vehicle widthdirection will be described following the flowchart indicating anaverage distance calculation routine illustrated in FIG. 8 . Thisaverage distance calculation routine is executed repeatedly for everyset time set in the travel_ECU 14 in a case where the host vehicle M istraveling on a road without a median strip, manual driving mode isselected as the driving mode, and preliminary collision avoidancecontrol is turned off.

When the routine starts, in step S001, the travel_ECU 14 recognizes, onthe basis of information input from the DMS of the HMI 31, the drivercurrently driving the host vehicle M.

In a subsequent step S002, the travel_ECU 14 reads the average distanceXave calculated to the present time in association with the recognizeddriver.

In a subsequent step S003, the travel_ECU 14 checks, on the basis of thetraveling environment information, whether the host vehicle M passed bythe oncoming moving body O.

Then, in step S003, in a case where the travel_ECU 14 determines thatthe host vehicle M did not pass by the oncoming moving body O (stepS003: NO), the travel_ECU 14 exits the routine.

On the other hand, in step S003, in a case where the travel_ECU 14determines that the host vehicle M passed by the oncoming moving body O(step S003: YES), the travel_ECU 14 proceeds to step S004.

In step S004, the travel_ECU 14 acquires the distance x between the hostvehicle M and the oncoming moving body O in the vehicle width direction.Note that, in some embodiments, this distance x in the vehicle widthdirection is a distance taking into consideration projections such asdoor mirrors of the host vehicle M and the oncoming moving body O (thatis, the distance between the projections such as the door mirrors of thehost vehicle M and the oncoming moving body O).

In a subsequent step S005, the travel_ECU 14 calculates a new averagedistance Xave including the distance x just acquired and the averagedistance Xave calculated to the present, and exits the routine.

Details of the preliminary collision avoidance control will now bedescribed following the flowchart of a preliminary collision avoidancecontrol routine illustrated in FIG. 9 . This preliminary collisionavoidance control routine is executed repeatedly for every set time inthe travel_ECU 14 in a case where the preliminary collision avoidancecontrol is on and the host vehicle M is traveling on a road without amedian strip.

When the routine starts, the travel _ECU 14, in step S101, checkswhether the oncoming moving body O is present in the oncoming lane.

Then, in step S101, in a case where the travel_ECU 14 determines thatthe oncoming moving body O is not present in the oncoming lane (stepS101: NO), the travel_ECU 14 exits the routine.

On the other hand, in step S101, in a case where the travel_ECU 14determines that the oncoming moving body O is present in the oncominglane (step S101: YES), the travel_ECU 14 proceeds to step S102.

In step S102, the travel_ECU 14 calculates the longitudinaltime-to-collision TTCz and the lateral time-to-collision TTCx for theoncoming moving body O.

In a subsequent step S103, the travel_ECU 14 calculates the risk degreeRc (cumulative value) for the oncoming moving body O. The calculation ofthe risk degree Rc is performed according to the flowchart of a riskdegree calculation subroutine illustrated in FIG. 10 , for example.

When the subroutine starts, the travel_ECU 14, in step S201, recognizesthe front wheel(s) of the oncoming moving body O in a case where theoncoming moving body O is a four-wheeled vehicle, a two-wheeled vehicle,or the like.

In a subsequent step S202, the travel_ECU 14 determines the center ofthe oncoming moving body O. That is, for example, in a case where theoncoming moving body O is a four-wheeled vehicle, the travel_ECU 14determines a center of treads of the front wheels recognized in stepS201 as the center of the oncoming moving body O. Further, for example,in a case where the oncoming moving body O is a two-wheeled vehicle, thetravel_ECU 14 determines the position of the front wheel recognized instep S201 as the center of the oncoming moving body O.

In a subsequent step S203, the travel_ECU 14 recognizes the width of theoncoming moving body O.

In a subsequent step S204, the travel_ECU 14 acquires the targettraveling path Rm set in the host vehicle M.

In a subsequent step S205, the travel_ECU 14 recognizes the drivercurrently driving the host vehicle M on the basis of information inputfrom the DMS of the HMI 31.

In a subsequent step S206, the travel_ECU 14 checks whether the averagedistance Xave associated with the recognized driver has been calculated.

Then, in step S206, in a case where the travel_ECU 14 determines thatthe average distance Xave associated with the driver has not beencalculated (step S206: NO), the travel_ECU 14 proceeds to step S209.

On the other hand, in step S206, in a case where the travel_ECU 14determines that the average distance Xave associated with the driver hasbeen calculated (step S206: YES), the travel_ECU 14 proceeds to stepS207.

In step S207, the travel_ECU 14 reads the average distance Xavecorresponding to the currently recognized driver.

In a subsequent step S208, the travel_ECU 14 sets an increase/decreasefor the risk determination reference region set in advance. Thisincrease/decrease ratio is set on the basis of the average distance Xavewith reference to a map or the like set in advance, for example.

Upon proceeding from step S206 or step S208 to step S209, the travel_ECU14 sets the risk determination region for the oncoming moving body O.For example, in a case where the increase/decrease ratio is not set(that is, in a case where the routine proceeds from step S206 to stepS209), the travel_ECU 14 sets, as the risk determination region for theoncoming moving body O, the risk determination reference region set inadvance. On the other hand, for example, in a case where theincrease/decrease ratio is set (that is, in a case where the routineproceeds from step S208 to step S209), the travel_ECU 14 sets, as therisk determination region for the oncoming moving body O, a riskdetermination region in which the width of the risk determinationreference region (each small region) is increased or decreased by theincrease/decrease ratio. In this way, the travel_ECU 14 sets the riskdetermination region for calculating the risk degree R that differs invalue depending on the distance outward from the center of the oncomingmoving body O in the width direction of the oncoming moving body O.

In a subsequent step S210, the travel_ECU 14 calculates the risk degreeR of the oncoming moving body O on the basis of the risk determinationregion. That is, the travel_ECU 14 calculates, as the risk degree R forthe oncoming moving body O, the risk degree R of the risk determinationregion to be penetrated by the target traveling path Rm of the hostvehicle M.

In a subsequent step S211, the travel_ECU 14 calculates the cumulativevalue of the risk degrees R to the present time (risk degree Rc) for theoncoming moving body O, and then exits the subroutine. That is, thetravel_ECU 14 calculates the cumulative risk degree Rc for the oncomingmoving body O by using equation (1) described above, for example.

In the main routine in FIG. 9 , upon proceeding from step S103 to stepS104, the travel_ECU 14 performs upper limit processing on the riskdegree Rc. This upper limit processing is, in a case where the riskdegree Rc is cumulatively calculated, processing for preventing the riskdegree Rc from becoming excessively large and for preventing the riskdegree Rc from becoming unnecessarily large due to a factor other thanthe wandering of the oncoming moving body O.

In this upper limit processing, the travel_ECU 14 basically limits therisk degree Rc to, for example, “9” or less. However, in a case wherethe risk degree Rc is expected to increase due to a factor other thanthe wandering of the oncoming moving body O, the travel_ECU 14 limitsthe risk degree Rc to, for example, “4” or less.

Upper limit processing for this risk degree Rc is executed according tothe flowchart of a risk degree upper limit processing subroutineillustrated in FIG. 11 , for example.

When the subroutine starts, the travel_ECU 14 acquires, in step S301,the target traveling path Rm set for the host vehicle M.

In a subsequent step S302, the travel_ECU 14 calculates the predictedtraveling path Ro of the oncoming moving body O on the basis of thecurrent velocity and movement direction of the oncoming moving body O.

In a subsequent step S303, the travel_ECU 14 calculates a predictedcollision point Pc and a collision angle θc of the host vehicle M andthe oncoming moving body O. For example, in a case where it is presumedthat the oncoming moving body O moved on a predicted traveling path Ro(refer to O′ in FIG. 4 ), the travel_ECU 14 calculates, as the predictedcollision point Pc of the host vehicle M and the oncoming moving body O,a point at which the longitudinal time-to-collision TTCz and the lateraltime-to-collision TTCx are both “0” or less (refer to FIG. 4 ), forexample. Further, in a case where it is presumed that the oncomingmoving body O moved to the predicted collision point Pc, the travel_ECU14 calculates the collision angle θc on the basis of a relative anglebetween the oncoming moving body O′ after moving and the host vehicle M.

In a subsequent step S304, the travel_ECU 14 checks whether a blinker ofthe oncoming moving body O is blinking.

Then, in step S304, in a case where the travel_ECU 14 determines that ablinker of the oncoming moving body O is blinking (step S304: YES), thetravel_ECU 14 proceeds to step S309.

In step S309, for example, the travel_ECU 14 performs upper limitprocessing in which the risk degree Rc is set to “4” or less, andsubsequently exits the subroutine.

That is, for example, as illustrated in FIG. 14 , as a case where therisk degree Rc of the oncoming moving body O increases due to a factorother than wandering, a case is expected where the oncoming moving bodyO turns toward the traveling lane of the host vehicle M while theblinker is blinking. In such a case, the intention of the driver drivingthe oncoming moving body O is clear, and it is expected that the driveris sufficiently aware of the host vehicle M. Accordingly, in such acase, it is hard to imagine sudden entry of the oncoming moving body Ointo the traveling lane of the host vehicle M at the timing at whichcollision with the host vehicle M is highly likely, and thus the controlcontent is restricted by upper limit processing.

On the other hand, in step S304, in a case where the travel_ECU 14determines that the blinker of the oncoming moving body O is notblinking (step S304: NO), the travel_ECU 14 proceeds to step S305.

In step S305, the travel_ECU 14 checks whether, compared with before,the behavior of the oncoming moving body O is changing into anadvantageous situation in which collision with the host vehicle M isavoidable. That is, the travel_ECU 14 checks whether the predictedtraveling path Ro of the oncoming moving body O calculated in step S302and the predicted collision point Pc and the collision angle θc of theoncoming moving body O calculated in step S303 are changing into anadvantageous situation. Here, for example, in a case where the lateralvelocity component Vox of the oncoming moving body O starts to decline,in general, the predicted traveling path Ro of the oncoming moving bodyO is angled toward the host vehicle M. Further, for example, in a casewhere the lateral velocity component Vox of the oncoming moving body Ostarts to decline, the predicted collision point Pc of the oncomingmoving body O moves to the host vehicle M. Further, for example, in acase where the lateral velocity component Vox of the oncoming movingbody O starts to decline, the collision angle θc changes so as toincrease. Thus, the travel_ECU 14 determines that the behavior of theoncoming moving body O has changed to be advantageous in a case where atleast one of the following is true: the predicted traveling path Ro isangled toward the host vehicle M, the predicted collision point Pc ismoved to the host vehicle M, or the collision angle θc is changed so asto increase.

Then, in a case where the travel_ECU 14 determines that the behavior ofthe oncoming moving body O has changed to be advantageous (step S305:YES), the travel_ECU 14 proceeds to step S309.

Upon proceeding to step S309, the travel_ECU 14 performs upper limitprocessing in which the risk degree Rc is set to “4” or less, forexample, and subsequently exits the subroutine.

On the other hand, in step S305, in a case where the travel_ECU 14determines that the behavior of the oncoming moving body O changed to bedisadvantageous (step S305: NO), the travel_ECU 14 proceeds to stepS306.

In step S306, the travel_ECU 14 checks whether a stationary object suchas a parked vehicle is present near the oncoming moving body O in theoncoming lane.

In step S306, in a case where the travel_ECU 14 determines that a parkedvehicle or the like is present in the oncoming lane (step S306: YES),the travel_ECU 14 proceeds to step S309.

Upon proceeding to step S309, the travel_ECU 14 performs upper limitprocessing in which the risk degree Rc is set to “4” or less, forexample, and subsequently exits the subroutine.

That is, as illustrated in FIG. 15 , for example, as a case where therisk degree Rc of the oncoming moving body O increases due to a factorother than wandering, a case is expected where the oncoming moving bodyO avoids a stationary object such as a parked vehicle in the oncominglane. In such a case, the intention of the driver driving the oncomingmoving body O is clear, and it is expected that the driver issufficiently aware of the host vehicle M. In addition, in such a case,it is expected that the risk degree R calculated on the basis of therisk determination region temporarily increases and subsequently startsto decrease quickly. Accordingly, in such a case, it is hard to imaginesudden entry of the oncoming moving body O into the traveling lane ofthe host vehicle M at the timing at which collision with the hostvehicle M is highly likely, and thus the control content is restrictedby upper limit processing.

On the other hand, in step S306, in a case where the travel_ECU 14determines that a parked vehicle or the like is not present in theoncoming lane (step S306: NO), the travel_ECU 14 proceeds to step S307.

In step S307, the travel_ECU 14 checks whether the oncoming moving bodyO is merging from a branch road into the oncoming lane.

Then, in step S307, in a case where the travel_ECU 14 determines thatthe oncoming moving body O is merging from a branch road (step S307:YES), the travel_ECU 14 proceeds to step S309.

Upon proceeding to step S309, the travel_ECU 14 performs upper limitprocessing in which the risk degree Rc is set to “4” or less, forexample, and subsequently exits the subroutine.

That is, for example, as illustrated in FIG. 16 , as a case where therisk degree Rc of the oncoming moving body O increases due to a factorother than wandering, a case is expected where the oncoming moving bodyO enters the oncoming lane from a branch road or the like. In such acase, the intention of the driver driving the oncoming moving body O isclear, and it is expected that the driver is sufficiently aware of thehost vehicle M. In addition, in such a case, it is expected that therisk degree R calculated on the basis of the risk determination regiontemporarily increases and subsequently starts to decrease quickly.Accordingly, in such a case, it is hard to imagine sudden entry of theoncoming moving body O into the traveling lane of the host vehicle M atthe timing of collision with the host vehicle M, and thus the controlcontent is restricted by upper limit processing.

On the other hand, in step S307, in a case where the travel_ECU 14determines that the oncoming moving body O is not merging from a branchroad (step S307: NO), the travel_ECU 14 proceeds to step S308.

Upon proceeding to step S308, the travel_ECU 14 performs upper limitprocessing in which the risk degree Rc is set to “9” or less, forexample, and subsequently exits the subroutine.

In the main routine in FIG. 9 , upon proceeding from step S104 to stepS105, the travel_ECU 14 performs reduction processing on the risk degreeRc. This reduction processing is processing for reducing, asappropriate, a risk level LV of preliminary collision avoidance control(described below) permitted in accordance with the risk degree Rc. Thisrisk level LV is reduced on the basis of a relative relationship betweenthe host vehicle M and the oncoming moving body O. For example, in acase where the risk degree Rc of the oncoming moving body O entering thetraveling lane of the host vehicle M is high because the wandering ofthe oncoming moving body O is significant; however the oncoming movingbody O is far away, the likelihood of the host vehicle M colliding withthe oncoming moving body O is low. Therefore, in such a case, thetravel_ECU 14 reduces the risk level LV of the preliminary collisionavoidance control permitted in accordance with the risk degree Rc toprevent excessive preliminary collision avoidance control from beingexecuted.

This reduction processing is executed according to the flowchart of areduction processing subroutine illustrated in FIG. 12 , for example.

When the subroutine starts, the travel_ECU 14 checks whether thelongitudinal time-to-collision TTCz for the oncoming moving body O isless than a fourth threshold value Tth4 (where, Tth1 < Tth4) set inadvance.

Then, in step S401, in a case where the travel_ECU 14 determines thatthe longitudinal time-to-collision TTCz is equal to or greater than thefourth threshold value Tth4 (step S401: NO), the travel_ECU 14 proceedsto step S402.

In step S402, the travel_ECU 14 permits preliminary collision avoidancecontrol corresponding to a case where the risk degree Rc is “2” or less,and subsequently exits the subroutine. In this way, the travel_ECU 14permits control up to preliminary collision avoidance controlcorresponding to a case where the risk degree Rc is “2” even in a casewhere the current risk degree Rc is “9,” for example. Further, in a casewhere the current risk degree Rc is “2,” for example, the travel_ECU 14permits the preliminary collision avoidance control corresponding to acase where the risk degree Rc is “2”. Note that, in the presentembodiment, preliminary collision avoidance control corresponding to acase where the risk degree Rc is “2” or less is collision avoidancecontrol for the risk level LV = 1 associated with the “caution region”of the risk determination region.

On the other hand, in step S401, in a case where the travel_ECU 14determines that the longitudinal time-to-collision TTCz is less than thefourth threshold value Tth4 (step S401: YES), the travel_ECU 14 proceedsto step S403.

In step S403, the travel_ECU 14 checks whether the longitudinaltime-to-collision TTCz is less than a fifth threshold value Tth5 (where,Tth1 ≤ Tth5 < Tth4) set in advance.

Then, in step S403, in a case where the travel_ECU 14 determines thatthe longitudinal time-to-collision TTCz is equal to or greater than thefifth threshold value Tth5 (step S403: NO), the travel_ECU 14 proceedsto step S404.

In step S404, the travel_ECU 14 permits preliminary collision avoidancecontrol corresponding to a case where the risk degree Rc is “4” or less,and subsequently exits the subroutine. In this way, the travel_ECU 14permits control up to preliminary collision avoidance controlcorresponding to a case where the risk degree Rc is “4” even in a casewhere the current risk degree Rc is “9,” for example. Further, in a casewhere the current risk degree Rc is “4,” for example, the travel_ECU 14permits preliminary collision avoidance control corresponding to a casewhere the risk degree Rc is “4”. Note that, in the present embodiment,preliminary collision avoidance control corresponding to a case wherethe risk degree Rc is greater than “2” and “4” or less is collisionavoidance control for the risk level LV = 2 associated with the “warningregion” of the risk determination region.

On the other hand, in step S403, in a case where the travel_ECU 14determines that the longitudinal time-to-collision TTCz is less than thefifth threshold value Tth5 (step S403: YES), the travel_ECU 14 proceedsto step S405.

In step S405, the travel_ECU 14 permits preliminary collision avoidancecontrol corresponding to a case where the risk degree Rc is “9” or less,and subsequently exits the subroutine. In this way, the travel_ECU 14permits preliminary collision avoidance control corresponding to allrisk degrees Rc, for example. That is, in a case where the current riskdegree Rc is “9,” for example, the travel_ECU 14 permits preliminarycollision avoidance control corresponding to a case where the riskdegree Rc is “9”. Further, in a case where the current risk degree Rc is“4,” for example, the travel_ECU 14 permits preliminary collisionavoidance control corresponding to a case where the risk degree Rc is“4”. Note that, in the present embodiment, preliminary collisionavoidance control corresponding to a case where the risk degree Rc isgreater than “4” and “9” or less is collision avoidance control for therisk level LV = 3 associated with the “danger region” of the riskdetermination region.

In the main routine in FIG. 9 , upon proceeding from step S105 to stepS106, the travel_ECU 14 performs a forced control interventiondetermination with respect to the oncoming moving body O. This forcedcontrol intervention is a determination for forcibly executingpreliminary collision avoidance control for the risk level LV = 3 in anemergency such as in a case where the oncoming moving body O continuesto move directly in the direction of the host vehicle M, for example.

This forced control intervention determination is made according to aforced control intervention determination subroutine illustrated in FIG.13 , for example.

When the subroutine starts, in step S501, the travel_ECU 14 checkswhether the oncoming moving body O has continued to move directly in thedirection of the host vehicle M for a set time (for example, apredetermined frame).

Then, in step S501, in a case where the travel_ECU 14 determines thatthe oncoming moving body O is not moving directly in the direction ofthe host vehicle M (step S501: NO), the travel_ECU 14 exits thesubroutine.

On the other hand, in step S501, in a case where the travel_ECU 14determines that the oncoming moving body O is moving directly in thedirection of the host vehicle M (step S501: YES), the travel_ECU 14proceeds to step S502.

In step S502, the travel_ECU 14 corrects the risk degree Rc for theoncoming moving body O to “9” and corrects the risk level LV permittedfor the oncoming moving body O to “3,” for example, and subsequentlyexits the subroutine.

In the main routine in FIG. 9 , upon proceeding from step S106 to stepS107, the travel_ECU 14 determines the kind of preliminary collisionavoidance action to be taken in response to the oncoming moving body O.This preliminary collision avoidance action is determined on the basisof the risk level LV currently permitted for the oncoming moving body Oand the current risk degree Rc currently set for the oncoming movingbody O, for example.

Herein, for example, as illustrated in FIG. 17 , in a case where thecurrent risk degree Rc for the oncoming moving body O is “0”, “0” is setas the risk level for the oncoming moving body O. In a case where therisk level LV = 0, the travel_ECU 14 prohibits output of an alert or thelike for notifying the driver of the presence of the oncoming movingbody O. Further, in the case where the risk level LV = 0, the travel_ECU14 prohibits avoidance control in the longitudinal direction (front-reardirection of the host vehicle M) in response to the oncoming moving bodyO. Furthermore, in the case where the risk level LV = 0, the travel_ECU14 prohibits avoidance control in the lateral direction (vehicle widthdirection of the host vehicle M) in response to the oncoming moving bodyO.

Further, for example, as illustrated in FIG. 17 , in a case where therisk degree Rc is greater than “0” and control up to the risk level LV =1 is permitted in response to the oncoming moving body O, the travel_ECU14 prohibits output of an alert or the like for notifying the driver ofthe presence of the oncoming moving body O.

Further, in a case where the risk degree Rc is greater than “0” andcontrol up to the risk level LV = 1 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe longitudinal direction (front-rear direction of the host vehicle M)in response to the oncoming moving body O. In this avoidance control,the travel_ECU 14 permits first acceleration suppression control, forexample, in place of braking control. In this first accelerationsuppression control, a first acceleration suppression amount is set, asappropriate, only in a case where the host vehicle M is accelerating(including a case where the host vehicle M is about to accelerate), forexample. The first acceleration suppression amount is set so as toincrease as the longitudinal time-to-collision TTCz decreases, on thebasis of a map or the like set in advance, for example.

Further, in a case where the risk degree Rc is greater than “0” andcontrol up to the risk level LV = 1 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe lateral direction (vehicle width direction of the host vehicle M) inresponse to the oncoming moving body O. In this avoidance control, thetravel_ECU 14 permits steering control within a range in which the hostvehicle M does not deviates from the traveling lane in which the hostvehicle M is traveling, for example. In this steering control, anavoidance amount by steering is set as appropriate. The avoidance amountis set so as to increase as the lateral time-to-collision TTCxdecreases, on the basis of a map or the like set in advance, forexample. Note that, in some embodiments, the steering wheel steeringspeed permitted for this steering control is limited to about 10 deg/s,for example.

Further, for example, as illustrated in FIG. 17 , in a case where therisk degree Rc is greater than “2” and control up to the risk level LV =2 is permitted in response to the oncoming moving body O, the travel_ECU14 sets an alert or the like for notifying the driver of the presence ofthe oncoming moving body O.

Further, in a case where the risk degree Rc is greater than “2” andcontrol up to the risk level LV = 2 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe longitudinal direction in response to the oncoming moving body O. Inthis avoidance control, the travel_ECU 14 permits second accelerationsuppression control in place of braking control. In this secondacceleration suppression control, a second acceleration suppressionamount is set as appropriate only in a case where the host vehicle M isaccelerating (including a case where the host vehicle M is about toaccelerate), for example. The second acceleration suppression amount isset so as to increase as the longitudinal time-to-collision TTCzdecreases, on the basis of a map or the like set in advance, forexample. Note that the second acceleration suppression amount is set tobe greater than the first acceleration suppression amount. For example,the deceleration (suppression amount) obtained when the driver releasesthe accelerator is provided as the upper limit for the secondacceleration suppression amount.

Further, in a case where the risk degree Rc is greater than “2” andcontrol up to the risk level LV = 2 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe lateral direction in response to the oncoming moving body O. In thisavoidance control, the travel_ECU 14 permits steering control to aposition at which the host vehicle M straddles a lane marker, forexample. In this steering control, the avoidance amount by steering isset as appropriate. The avoidance amount is set so as to increase as thelateral time-to-collision TTCx decreases, on the basis of a map or thelike set in advance, for example. Note that, in some embodiments, thesteering wheel steering speed permitted for this steering control islimited to about 80 deg/s, for example.

Further, for example, as illustrated in FIG. 17 , in a case where therisk degree Rc is greater than “4” and control up to the risk level LV =3 is permitted in response to the oncoming moving body O, the travel_ECU14 sets an alert or the like for notifying the driver of the presence ofthe oncoming moving body O.

Further, in a case where the risk degree Rc is greater than “4” andcontrol up to the risk level LV = 3 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe longitudinal direction in response to the oncoming moving body O. Inthis avoidance control, the travel_ECU 14 permits braking control. Inthis braking control, for example, the braking amount is set asappropriate. The braking amount is set so as to increase as thetime-to-collision TTCz decreases, on the basis of a map or the like setin advance. Note that this braking amount is, in one example, set withthe first target deceleration a1 (0.4 G, for example) of the emergencycollision avoidance control described above as the limit.

Further, in a case where the risk degree Rc is greater than “4” andcontrol up to the risk level LV = 3 is permitted in response to theoncoming moving body O, the travel_ECU 14 performs avoidance control inthe lateral direction in response to the oncoming moving body O. In thisavoidance control, the travel_ECU 14 permits steering control to aposition at which the host vehicle M travels across a lane marker, forexample. In this steering control, the avoidance amount by steering isset as appropriate, for example. The avoidance amount is set so as toincrease as the lateral time-to-collision TTCx decreases, on the basisof a map or the like set in advance, for example. Note that, in someembodiments, the steering wheel steering speed permitted for thissteering control is limited to about 240 deg/s, for example.

Upon proceeding from step S107 to step S108, the travel_ECU 14 checkswhether control intervention is used in response to the oncoming movingbody O, that is, checks whether a predetermined control amount has beenset in step S107 described above.

Then, in step S108, in a case where the travel_ECU 14 determines thatcontrol intervention is not used (step S108: NO), the travel_ECU 14exits the routine.

On the other hand, in a case where the travel_ECU 14 determines thatcontrol intervention is used in step S108 (step S108: YES), thetravel_ECU 14 proceeds to step S109.

In step S109, the travel_ECU 14 checks whether the oncoming moving bodyO has entered the target traveling region Am of the host vehicle M.

Then, in step S109, in a case where the travel_ECU 14 determines thatthe oncoming moving body O is present outside the target travelingregion Am of the host vehicle M (step S109: NO), the travel_ECU 14proceeds to step S110.

In step S110, the travel_ECU 14 executes preliminary collision avoidancecontrol, and subsequently exits the routine. That is, the travel_ECU 14executes preliminary collision avoidance control on the basis of thecontrol amount set in step S107.

On the other hand, in step S109, in a case where the travel_ECU 14determines that the oncoming moving body O is present inside the targettraveling region Am of the host vehicle M (step S109: YES), thetravel_ECU 14 proceeds to step S111.

In step S111, the travel_ECU 14 transitions the control in response tothe oncoming moving body O from preliminary collision avoidance controlto emergency collision avoidance control, and then exits the routine.

According to such an embodiment, the travel_ECU 14 recognizes theoncoming moving body O on the basis of the traveling environmentinformation. Further, the travel _ECU 14 sets the risk determinationregion for calculating the risk degree that decreases as the distanceoutward from the center of the oncoming moving body O in the widthdirection of the oncoming moving body O increases. Furthermore, thetravel_ECU 14 calculates the risk degree Rc for the oncoming moving bodyO in accordance with the overlap state of the target traveling path Rmof the host vehicle M and the risk determination region. Then, thetravel_ECU 14 recognizes the oncoming moving body O as an obstacle inaccordance with the risk degree Rc, and performs preliminary collisionavoidance control prior to emergency collision avoidance control inresponse to the oncoming moving body O recognized as the obstacle.

As a result, sufficient safety can be ensured even in a case where theoncoming moving body O, such as an oncoming vehicle, suddenly enters thetraveling lane of the host vehicle M. That is, the travel_ECU 14performs preliminary collision avoidance control in accordance with therisk degree Rc in response to the oncoming moving body O before theoncoming moving body O enters the target traveling region Am of the hostvehicle M. Accordingly, even in a case where the oncoming moving body Osuddenly travels across the lane marker and enters in front of the hostvehicle M, the emergency collision avoidance control can be performedwith well-prepared state.

In this case, in a case where the preliminary collision avoidancecontrol is turned off (in one example, in a case where the host vehicleM is traveling on a road without a median strip, the manual driving modeis selected as the driving mode, and the preliminary collision avoidancecontrol is turned off), the travel_ECU 14 acquires the distance xbetween the host vehicle M and the oncoming moving body O in the vehiclewidth direction every time the host vehicle M passes by the oncomingmoving body O. Further, the travel_ECU 14 calculates the averagedistance Xave of the distance x in the vehicle width direction. Then, ina case where the preliminary collision avoidance control is on, thetravel_ECU 14 variably sets the risk determination region so that therisk degree R calculated from the risk determination region becomes “0”in a case where the distance x between the host vehicle M and theoncoming moving body O in the vehicle width direction matches theaverage distance Xave. This can prevent the risk degree R (risk degreeRo) from deviating from the feeling of the driver, and achieve thepreliminary collision avoidance control that matches the feeling of thedriver.

Further, the travel_ECU 14 calculates the risk degree Rc by a cumulativecalculation with a predetermined weight applied to the current riskdegree R and the past risk degrees R calculated on the basis of the riskdetermination region for the oncoming moving body O. In this way, thestable risk degree Rc can be calculated even in a case where theoncoming moving body O is meandering by wandering or the like and therelationship between the risk determination region and the targettraveling path Rm of the host vehicle M fluctuates. Accordingly, therisk due to wandering or the like of the oncoming moving body O can beaccurately determined, and appropriate preliminary collision avoidancecontrol can be achieved.

In addition, the travel_ECU 14 performs upper limit processing on therisk degree Rc cumulatively calculated. This can prevent the risk degreeRc from becoming excessively large, and suppress unnecessary preliminarycollision avoidance control.

Further, the travel_ECU 14 varies the control level (risk level)permitted to the preliminary collision avoidance control in accordancewith the value of the longitudinal time-to-collision TTCz. This makes itpossible to achieve appropriate preliminary collision avoidance controlin response to the oncoming moving body O.

Herein, in the embodiment described above, the image recognition_ECU 13,the travel_ECU 14, the CP_ECU 21, the E/G_ECU 22, the T/M_ECU 23, theBK_ECU 24, the PS_ECU 25 and the like are each constituted by a knownmicrocomputer including a central processing unit (CPU), a read accessmemory (RAM), a read only memory (ROM), a non-volatile storage unit, andthe like, and peripheral devices thereof. In the ROM, fixed data such asprograms executed by the CPU and data tables or the like are stored inadvance. Note that all or some of the functions of the processor may beconfigured by a logic circuit or an analog circuit. Further, theprocessing of the various kinds of programs may be realized by anelectronic circuit such as a field-programmable gate array (FPGA).

The disclosure described in the above embodiments is not limited to theembodiments, but in addition, various modifications can be made withoutdeparting from the spirit and scope of the invention in animplementation stage. Furthermore, the above embodiments includetechnologies in various stages and various kinds of technologies can beextracted with an appropriate combination of disclosed configurationrequirements.

For example, in a case where several configuration requirements aredeleted from all configuration requirements disclosed in the aboveembodiments, if the mentioned problems can be solved and theadvantageous effects can be achieved, the configuration from which theconfiguration requirements are deleted can be extracted as a technology.

1. A vehicle driving assist device comprising: a traveling environmentrecognizer configured to recognize traveling environment informationoutside a vehicle; an obstacle recognizer configured to recognize, basedon the traveling environment information, an obstacle present on atarget traveling path of the vehicle; an emergency collision avoidancecontroller configured to, upon determination that the vehicle is highlylikely to collide with the obstacle, perform emergency collisionavoidance control for avoiding a collision of the vehicle with theobstacle; an oncoming moving body recognizer configured to recognize,based on the traveling environment information, oncoming moving bodiesand an oncoming moving body each of which moves in an oncoming laneadjacent to a traveling lane of the vehicle and each of which has avelocity component in a direction opposite to a traveling direction ofthe vehicle; a risk determination region setting unit configured to seta risk determination region for calculating a risk degree that decreasesas a distance outward from a center of the oncoming moving body in awidth direction of the oncoming moving body increases; a risk degreecalculator configured to calculate the risk degree for the oncomingmoving body in accordance with an overlap state between the targettraveling path of the vehicle and the risk determination region; apreliminary collision avoidance controller configured to recognize theoncoming moving body as the obstacle in accordance with the risk degree,and perform preliminary collision avoidance control in response to theoncoming moving body recognized as the obstacle prior to the emergencycollision avoidance control; and an average distance calculatorconfigured to, when the preliminary collision avoidance control isturned off, acquire distances in a vehicle width direction between thevehicle and the oncoming moving bodies every time the vehicle passes bythe oncoming moving bodies, and calculate an average distance of thedistances in the vehicle width direction, wherein the risk determinationregion setting unit is further configured to set the risk determinationregion such that the risk degree calculated by the risk degreecalculator is zero at a distance in the vehicle width direction betweenthe vehicle and the oncoming moving body matching the average distance.2. The vehicle driving assist device according to claim 1, wherein therisk degree calculator is configured to calculate, for the oncomingmoving body, a cumulative value obtained by performing weighting on therisk degree up to a present time, and the preliminary collisionavoidance controller is configured to perform the preliminary collisionavoidance control in response to the oncoming moving body in accordancewith the cumulative value of the risk degree.
 3. The vehicle drivingassist device according to claim 2, wherein the risk degree calculatoris configured to perform upper limit processing in which a preset valueis set as an upper limit of the cumulative value of the risk degree. 4.The vehicle driving assist device according to claim 1, wherein thepreliminary collision avoidance controller is configured to vary acontrol level permitted for the preliminary collision avoidance controlbased on a relative distance and a relative velocity of the vehicle andthe oncoming moving body in a front-rear direction.
 5. The vehicledriving assist device according to claim 2, wherein the preliminarycollision avoidance controller is configured to vary a control levelpermitted for the preliminary collision avoidance control based on arelative distance and a relative velocity of the vehicle and theoncoming moving body in a front-rear direction.
 6. The vehicle drivingassist device according to claim 3, wherein the preliminary collisionavoidance controller is configured to vary a control level permitted forthe preliminary collision avoidance control based on a relative distanceand a relative velocity of the vehicle and the oncoming moving body in afront-rear direction.
 7. A vehicle driving assist device comprising oneor more ECUs configured to recognize traveling environment informationoutside a vehicle, recognize, based on the traveling environmentinformation, an obstacle present on a target traveling path of thevehicle, upon determination that the vehicle is highly likely to collidewith the obstacle, perform emergency collision avoidance control foravoiding a collision of the vehicle with the obstacle, recognize, basedon the traveling environment information, oncoming moving bodies and anoncoming moving body each of which moves in an oncoming lane adjacent toa traveling lane of the vehicle and each of which has a velocitycomponent in a direction opposite to a traveling direction of thevehicle, set a risk determination region for calculating a risk degreethat decreases as a distance outward from a center of the oncomingmoving body in a width direction of the oncoming moving body increases,calculate the risk degree for the oncoming moving body in accordancewith an overlap state between the target traveling path of the vehicleand the risk determination region, recognize the oncoming moving body asthe obstacle in accordance with the risk degree, and perform preliminarycollision avoidance control in response to the oncoming moving bodyrecognized as the obstacle prior to the emergency collision avoidancecontrol, and acquire, when the preliminary collision avoidance controlis turned off, distances in a vehicle width direction between thevehicle and the oncoming moving bodies every time the vehicle passes bythe oncoming moving bodies, and calculate an average distance of thedistances in the vehicle width direction, wherein the one or more ECUsare further configured to set the risk determination region such thatthe risk degree is zero at a distance in the vehicle width directionbetween the vehicle and the oncoming moving body matching the averagedistance.